The present invention generally pertains to injection molding of a tie that is useful for forming a loop for retaining a bundle of elongated articles, such as cables. Such a tie is commonly known as a cable tie. The present invention is particularly directed to removal from the mold of a tie having at least one tooth on an abutment surface in the locking head of the tie.
One type of tie includes an elongated tongue with two ends and two broad sides, a locking head at one end of the tongue, a tip at the other end of the tongue, a first set of ratchet teeth extending along one broad side of the tongue and a second set of ratchet teeth extending along the other broad side of the tongue, wherein the locking head has sides defining a continuously bounded opening for receiving the tip of the tongue, the sides including a movable pawl that is hinged at one side of the opening and an abutment surface that is across the opening from the pawl, wherein the pawl has at least one pawl tooth disposed for engaging the first set of ratchet teeth when the tip of the tongue has been inserted through the opening with the first set of ratchet teeth facing the pawl, wherein the pawl, when the at least one pawl tooth is so engaged, is movable toward the abutment surface in response to pressure applied to the tongue in a direction opposite to the direction of insertion in order to force the second set of ratchet teeth against the abutment surface; and wherein at least one tooth is disposed on the abutment surface for engaging the second set of ratchet teeth when the tip of the tongue has been inserted through the opening with the second set of ratchet teeth facing the abutment surface and the side of the tongue including the second set of ratchet teeth is forced against the abutment surface by movement of the pawl. Such a tie is described in U.S. Pat. No. 4,473,524 to Paradis.
A prior art method of injection molding such a tie includes the steps of:
(a) providing a mold that includes mold parts for defining a cavity between the mold parts in the general shape of the tie; PA1 (b) injecting molten plastic material into the mold cavity; PA1 (c) solidifying the plastic material in the mold cavity to form the tie; PA1 (d) separating the mold parts to enable removal of the tie from the mold; and PA1 (e) removing the tie from the mold. PA1 (a) providing a mold that includes mold parts for defining a cavity between the mold parts in the general shape of the tie; PA1 (b) injecting molten plastic material into the mold cavity; PA1 (c) solidifying the plastic material in the mold cavity to form the tie; PA1 (d) separating the mold parts to enable removal of the tie from the mold; and PA1 (e) removing the tie from the mold; PA1 (f) moving the core to thereby enable the abutment wall to flex in a direction away from the pawl into a space vacated by movement of the core so that the tie can be removed from the mold pursuant to step (e) without significantly damaging the at least one abutment surface tooth.
When such a tie is formed by injection molding, it is difficult to remove the tie from the mold without significantly damaging the at least one tooth on the abutment surface unless the apex of the tooth is defined at a parting line between mold parts because the portion of the mold part that defines the abutment surface has a lateral dimension that is broader than the space between such tooth and the pawl, whereby withdrawal of such mold part from a parting line between mold parts compresses and thereby distorts such tooth.